U.S. Pat. No. 4,155,758 has disclosed a metal halide lamp with ceramic discharge vessel, in which a leadthrough is provided with a portion which is widened outside the discharge vessel. The external diameter of this portion is equal to the external diameter of the discharge vessel. A sealing frit is inserted as a ring between the end of the discharge vessel and the widened portion. A discharge-side part of the pin is formed from W, while the part remote from the discharge consists of Mo. This part is completely surrounded by a filling filament which reduces the dead volume. The standard joining technique for the two electrode parts is in this case welding or brazing.
US2005029949 and corresponding WO 03/060951 have disclosed a metal halide lamp with ceramic discharge vessel, in which a leadthrough in two-part form comprises an outer Nb pin and an inner part of the same diameter. The inner part consists of Mo5(Si,X)3, where X═B, Al, N or C.